Alk(en)yl and hydroxy-substituted aromatic acid modified epoxy resins

ABSTRACT

Modified epoxy resins are obtained by reaction of an epoxy resin with up to one mol equivalent per epoxy group of an alkyl or alkenyl substituted, hydroxy substituted aromatic acid, especially by reaction of a bisphenol A epoxy resin with an alkylated salicylic acid. Also are described a process for the production of such modified resins, curable compositions comprising the modified epoxy resin and products provided with the cured composition, especially in coating applications and civil engineering applications.

The present invention relates to modified epoxy resins obtainable byreaction of an epoxy resin with an alkyl or alkenyl substituted, hydroxysubstituted aromatic acid, to a process for the production of suchmodified resins, to curable compositions comprising the modified epoxyresin and to products provided with the cured composition, especially incoating applications and civil engineering applications.

To protect metal surfaces of for instance ships, bridges, aircraft's andbuilding structures usually high-performance coatings are used whichhave to be resistant to the corrosive effects of water, oxygen, solventsand any other corrosive agents which might come into contact with thecoated surfaces. Nowadays, coatings, usually ambient temperaturecoatings, with the required properties can be obtained by usingsolvent-borne, two-package epoxy coating systems, comprising especiallyglycidyl ethers of polyphenols, more particularly bisphenol A basedglycidyl compounds, which are cured with for instance polyamine,polyamide, polyamidoamine (or polyaminoamides), polyamidoadduct andpolyaminoadduct curing agents, as described in for instance The Handbookof Epoxy Resins by H. Lee and K. Neville, McGraw-Hill, New York (1967),Epoxy Resins, Chemistry and Technology, edited by C. A. May, MarcelDekker (1988) and Chemistry and Technology of Epoxy Resins, edited by B.Ellis, Blackie Academic & Professional (1993), incorporated herein byreference. Additives as pigments, fillers, extenders, surfaceactivators, thickeners, diluents, accelerators etc. may be used.

The above described systems, however, suffer from a number of drawbacks.The use of solvent-borne systems results in the evaporation of organicsolvents, which is from an environmental point of view highly undesired.Further, the use of amine curing agents, especially at low temperatures(0°-10° C.) and/or high humidity, often results in the occurrence ofundesired effects as blooming and/or haziness, due to reaction withcarbon dioxide and the presence of water and/or water vapour. Further,incomplete cure may occur, resulting in tacky films. Anotherdisadvantage of quite a large number of commercially available systemsis that the over-coatability is poor. This may be caused by a low curingspeed and/or the occurrence of blooming and/or haziness.

It has now been found that modification of epoxy resins with alkyl oralkenyl substituted, hydroxy substituted aromatic acid results in epoxyresins which in combination with suitable curing agents result incoatings having superior properties, while the disadvantages of theabove described systems do not occur. No volatile organic solvents needto be used, thus no environmental objections. The modified resins, incombination with a nitrogen based curing agent, e.g. polyamine,polyamide, polyamidoamine and/or polyaminoadduct curing agent, do notshow undesired effects as blooming and/or haziness, even not when usedat high humidity conditions and/or low temperature. Further, it hasappeared that very acceptable cure rates are obtained even at relativelylow temperatures (0° to 5° C.), which is quite exceptional. It will beappreciated that this is a major advantage of the modified resins of thepresent application. When used for coating applications, the layers areovercoatable after 12 to 24 hours. An additional advantage of the newresins is further that no crystallisation occurs, even not when storedfor prolonged periods at lower temperatures (below 25° C., especiallybetween 0° to 10° C.), a problem which often occurs with standard epoxyresins and compositions.

The present invention, therefore, relates to modified epoxy resinsobtainable by reaction of an epoxy resin with up to one mol equivalentper epoxy group of an alkyl or alkenyl substituted, hydroxy substitutedaromatic acid.

Reaction of epoxy compounds with (alkyl)substituted hydroxybenzoic acidsare already known from U.S. Pat. No. 3,789,044. However, as described incolumn 6, lines 37 to 65, the epoxide-containing materials should bereacted with a stoichiometric amount of hydroxybenzoic acid, asotherwise unreacted epoxide rings will be present in the compositionformed. In the examples only stoichiometric amounts of both reactantsare used. The reaction is carried out at temperatures above 148.9° C.(300° F.), see column 7, line 23. It is in this respect observed thatthe curing agent used in this reference is an isocyanate, which is acuring agent which reacts with hydroxy groups rather than epoxy groups.In the compositions according to the present invention, usually nitrogenbased curing agents as described above are used, i.e. curing agent whichwill react with epoxy groups.

The substituted aromatic acid to be used in the present invention issuitably a mono-alkyl, mono-hydroxy substituted benzoic or naphtoicacid, more particularly a substituted benzoic acid, especially a mono-or di-alkyl substituted benzoic acid, more especially a monoalkylsubstituted salicylic acid, or a mixture of monoalkyl and dialkylsubstituted benzoic acid in which the mono-alkyl compound is the maincompound. A certain amount of dicarboxylic acid, e.g. up to 25 molpercent, especially up to 15 mol percent, based on correspondingmonocarboxylic acids may be present. The alkyl substituent is preferablya straight or branched alkyl group comprising two to thirty-two carbonatoms, especially six to twenty-four, more especially ten to twenty. Amore preferred range is 14 to 18 carbon atoms. A very much preferredsubstituted benzoic acid is a mixture of predominantly monoalkylsubstituted salicylic acid obtained by alkylation of phenol with analpha-olefin, especially an olefin having from 14 to 18 carbon atoms,which olefin suitably may be obtained by oligomerisation of ethylene,followed by carboxylation of the alkylated phenol. Suitable processes toprepare such alkylated salicylic acids are described in for instance UK586461, UK 1146925 and EP 370555. The amount of mono-alkyl salicylicacid is usually between 60 and 90 percent, mostly straight chain alkylgroups substituted at the one or three-alkyl position at the orthoposition of the hydroxy group of the aromatic ring.

The amount of substituted aromatic acid is suitably up to 60 mol percentper epoxy group, preferably between 10 and 40 mol percent, morepreferably about 20 mol percent.

The epoxy resins used as starting material in the present inventiongenerally have an average of more than one, suitably at least 1.5,preferably at least 1.7, reactive 1,2-epoxy groups per molecule. Theseepoxy compounds generally have an average of up to 6, preferably up to4, more preferably up to 2.5, reactive 1,2-epoxy groups per molecule.These epoxy compounds can be monomeric or polymeric, saturated orunsaturated, aliphatic, cycloaliphatic, aromatic or heteroaromatic andmay be substituted, if desired, with other substituents in addition tothe epoxy groups, e.g. hydroxyl groups, alkoxyl groups or halogen atoms,especially bromine atoms. Further, reactive diluents, especiallymono-epoxy compounds may be added to the reaction mixture, especially tolower the viscosity.

Suitable epoxy compounds are the reaction products of polyphenols andepihalohydrins, polyalcohols and epihalohydrins, amines andepihalohydrins, sulphur containing compounds and epihalohydrins,polycarboxylic acids and epihalohydrins or mixtures thereof.

Preferred epoxy compounds are the reaction products of polyphenols andepihalohydrins, of polyalcohols and epihalohydrins, polycarboxylic acidsand epihalohydrins or mixtures thereof, the reaction products ofpolyphenols and epihalohydrins especially preferred. Illustrativeexamples of epoxy compounds are described in for instance The Handbookof Epoxy Resins by H. Lee and K. Neville, McGraw-Hill, New York (1967),Epoxy Resins, Chemistry and Technology, edited by C. A. May, MarcelDekker (1988) and Chemistry and Technology of Epoxy Resins, edited by B.Ellis, Blackie Academic & Professional (1993).

Epoxy compounds of particular interest in the practice of the presentinvention include diglycidyl ethers of bisphenol compounds, particularlythose compounds represented by general formula I, ##STR1## wherein eachA independently is a divalent hydrocarbon group having 1 to 8 carbonatoms, preferably methylene or isopropylidene, --C(O)--, --O--, --S--,--S--S--, --S(O)--, --S(O)₂ -- or a covalent bond, each X independentlyis hydrogen, an alkyl group having 1 to 4 carbon atoms, preferablymethyl, or halogen, preferably chlorine or bromine, and n has an averagevalue of 0 to 12, preferably 0 to 2. More preferably A is isopropylene,X is hydrogen or bromine, especially hydrogen, and n is up to 0.2.

The average epoxy equivalent weight is from 140, preferably from 170, upto about 3000, preferably up to 950, more preferably up to about 450.

Especially preferred examples of the epoxy compounds are bisphenol A andbisphenol F, especially bisphenol A, type epoxy compounds having anaverage epoxy equivalent weight of from 160 to 200. They arecommercially available from Shell Chemicals Europe under the trade namesEPIKOTE 828, 862 and 806. Further especially preferred examples arebrominated bisphenol A compounds which for example have an epoxyequivalent of from 200 to 800.

Further useful epoxy compounds are epoxy novolac resins. The epoxynovolac resins can be obtained by reacting, preferably in the presenceof a basic catalyst, e.g. sodium or potassium hydroxide, anepihalohydrin, e.g. epichlorohydrin, with the resinous condensate of analdehyde, e.g. formaldehyde, and either a monohydric phenol, e.g. phenolitself, or a polyhydric phenol. Further details concerning the natureand preparation of these epoxy novolacs resins can be obtained in thethree general references mentioned above. A suitable phenol-formaldehydeepoxy novolac resin is EPIKOTE 155 available from Shell ChemicalsEurope.

The above-mentioned epoxy compounds can be obtained by means known forthe preparation of epoxy resins from a compound containing hydroxylgroups by reacting such compounds with an epihalohydrin in the presenceof a suitable catalyst and reacting the resultant intermediatehalohydrin ether with a basic acting substance such as an alkali metalhydroxide. It has to be observed that many of the usual epoxy compoundsto be used for the production of the modified resins of this inventionwill be commercially available.

The modified resins of the present invention may be prepared by reactionof an epoxy resin with an alkyl or alkenyl substituted hydroxysubstituted aromatic acid. The reaction is suitably carried out between100° and 200° C., preferably between 140° and 180° C., for a timesufficient to complete the desired reaction, which is suitably from 0.25to 8 hours, more suitably from 0.5 to 6 hours, preferably between 2 and4 hours. At the lower temperatures longer reaction times are requiredwhereas at the higher temperatures less reaction time is required tocomplete the reaction. At temperatures above 200° C. and at the longerreaction times undesired reactions may occur, while at temperaturesbelow 100° C. the reaction times become very long, which may beinconvenient. The reaction can be conducted at any suitable pressurefrom subatmospheric to superatmospheric, e.g. from 0.1 to 10 bar.Atmospheric pressure is preferred. The reaction is preferably carriedout until essentially all alkyl substituted, hydroxy substitutedaromatic acid as initially present in the reaction mixture have reacted.Essentially all substituted benzoic acid has reacted when no free acidcan any more be detected in the reaction mixture. In that case at least90, usually at least 95 mol percent of the acid has reacted. Thereaction may be carried out by addition of the epoxy compound to thearomatic acid, by addition of the aromatic acid to the epoxy compound,by mixing the two reactants followed by reacting or combinationsthereof.

The reaction may be carried out with or without solvent. Solvent may beused especially when the reaction is carried out at a relatively lowtemperature. In the case a solvent is used aromatic solvents and/orketones can be used. The reaction can be carried out in the presence ofa suitable catalyst for conducting the reaction between an epoxy groupand a carboxylic acid group. In practice usually a catalyst is used. Forgeneral information about solvents and catalysts reference is made tothree references discussed above. Suitable such catalysts are acid andbase catalysts, for instance Lewis acid catalysts and metal saltcatalysts, more specifically tertiary amines, quaternary ammonium andphosphonium compounds and metal salts, especially of organic acids.Suitable tertiary amine catalysts include, for example, triethylamine,tributylamine, benzyldimethylamine, tris(dimethylaminomethyl)phenol,dimethylethanolamine, n-methylmorpholine, and combinations thereof.Suitable quaternary ammonium compounds are benzyl trimethyl ammoniumchloride, Suitable phosphonium compounds include, for example, ethyltriphenyl phosphonium salts, tetrabutyl phosphonium salts andcombinations thereof. Suitable metal salts of organic acids are forexample stannous salts of carboxylic acids as octanoic acid. The amountof catalyst to be employed is that amount which will effectivelycatalyse the reaction between the epoxy resin and the monocarboxylicacid. The specific amount of catalyst will depend upon the particularreactants and the catalyst being employed. Generally the catalyst isemployed in amounts between 0.1 to 100 ppm weight, especially between 1and 10 ppm, based on epoxy resin.

The modified epoxy resins of the present invention can be cured with anysuitable cross-linking agent such as a polyamine, polyamide,polyamidoamine and polyaminoadduct, a polycarboxylic acid or anhydridethereof or a polyphenolic compound. In this respect also reference ismade to the three general references mentioned above. Suitable examplesinclude primary and secondary polyamines, carboxylic acids andanhydrides thereof, phenolic hydroxyl-containing compounds, guanidine's,biguanidine's, polyamides, Mannich bases, ketimines, oxazolines andcombinations thereof. The polyaminoadduct embraces the reaction of analiphatic primary polyamine with one of the following reactants: alkylmonoepoxides, diepoxides, ethylene oxide, propylene oxide,acrylonitrile, aldehydes (thereby forming Schiff's bases), ketones, ormetallic salts of organic or inorganic acids. Particularly suitablecuring agents include, for example, ethylene diamine,diethylenetriamine, triethylenetetramine, dicyandiamide,diaminocyclohexane, adipic acid, phosphoric acid or combinationsthereof. Many of the suitable curing agents are commercially available.The curing agents are employed in an amount which will effectively curethe composition containing the modified epoxy resin. These amounts willdepend upon the particular epoxy resin and the curing agent employed.Suitable amounts are from 0.4 to 1.2, suitably from 0.6 to 1.1, moresuitably from 0.8 to 1.0, most suitably about 1 equivalent of curingagent per epoxide equivalent for those curing agents which cure byreacting with the epoxy group of the epoxy resin. The Handbook of EpoxyResins and the other two references mentioned above contain variousdiscussions concerning the curing of epoxy resins as well as acompilation of suitable curing agents.

If desired, the thermosettable compositions of the present invention canbe blended with other materials such as solvents or (reactive) diluents,fillers, pigments, dyes, flow modifiers, thickeners, anti-foamersreinforcing agents, fire retarding or suppressing agents andcombinations thereof. These additives are added in functionallyequivalent amounts, e.g. the pigments and/or dyes are added inquantities which will provide the composition with the desired colour.Suitably the amount of additives is from 0 to 150 percent by weight,especially 20 to 100 percent, based upon the combined weight of theepoxy resin and the curing agent. Solvents and diluents which can beemployed herein include, for example, hydrocarbons, ketones, glycolethers, glycolether acetates and combinations thereof. A solvent, e.g.an aromatic solvent, especially xylene, or a diluent may be used tomodify the viscosity. Each of the modifiers such as thickeners, flowmodifiers and the like can be employed suitably in amounts of from 0.05to 5, especially 0.1 to 3 percent by weight based upon the combinedweight of epoxy resin and curing agent. Reinforcing materials which canbe employed herein include natural and synthetic fibres in the form ofwoven, mat, monofilament, chopped fibres and the like, Suitablereinforcing materials include glass, ceramics, nylon, rayon, cotton,aramid, graphite and combinations thereof. Suitable fillers which can beemployed include, for instance, inorganic oxides, inorganic carbonates,ceramic microspheres, plastic microspheres, glass microspheres, clay,sand. gravel and combinations thereof. The fillers can be used inamounts suitably from 0 to 100, especially 10 to 60 percent by weightbased upon the combined weight of epoxy resin and curing agent.

The modified epoxy resins of the present invention can be formulated foruse in such applications as, for instance, coating, flooring, casting,crack repair, moulding, adhesives, potting, filament winding,encapsulation, structural and electrical laminates, composites and thelike.

The modified epoxy resins are especially suitable for use in coatingapplications. In that case the starting epoxy resin is especially aliquid resin, a semi solid epoxy resin or epoxy resin solution,especially a bisphenol A based resin, while the curing agent is apolyamine, polyamide, polyaminoamide or amineadduct. These coatingcompositions can be used at relatively low temperatures, e.g. from -25°C. to 25° C., especially from -5° to 20° C., at relatively highhumidity, e.g. from 50 to 95 percent r.h., especially from 60 to 90percent r.h. Coating applied at lower temperature show excellentproperties with respect to the complete absence of blooming and/orhaziness, and are overcoatable after 6 to 24 hours, usually alreadyafter 8 to 12 hours. The coating compositions can be applied byconventional coating methods such as brush-coating and spray coating.Curing can generally be carried out by exposure of the appliedcomposition to ambient conditions for one hour to one week.

Coating compositions according to the invention may be provided as atwo-container system. The first container contains the modified epoxyresin component and the second container contains the curing agent forthe epoxy resin. Any diluents used may be incorporated into eithercontainer, although any amine reactive diluents are preferably providedwith the resin component.

The following examples illustrate the present invention. Unlessotherwise mentioned, all parts and percentages are weight parts andweight percentages.

EXAMPLE 1

EPIKOTE 828, a bisphenol A based epoxy resin available from ShellChemicals Europe, 500 g, a mixture of 3-alkyl substituted salicylicacids in which the alkyl group contained from 14 to 18 carbon atoms, 327g (20 mol percent per epoxy group), and ethyltriphenylphosphoniumiodide, 0.15 g, were mixed together. The reaction temperature wasincreased to 175° C. (heating up to 110° C. in 30 minutes, 30 minutes at110° C., heating to 175° C. in 60 minutes, 30 minutes at 175° C., totalreaction time 2.5 hours). After cooling the modified resin was obtained.

EXAMPLES 2-4

Example 1 was repeated, but different final reaction temperatures wereused to prepare modified resins. The reaction times were kept the same.EPIKOTE 828EL, a commercially available resin, was used as startingresin. It will be clear that due to the lower viscosity of the products,these products now can be used in certain applications without solventor with less solvent.

    ______________________________________                                                               Final EGC                                                                              Viscosity                                     Example  Temperature   (mmol/kg)                                                                              (Pa.s)                                        ______________________________________                                        2        175           2288     2.76                                          3        140           2385     2.42                                          4        110           2488     2.08                                          ______________________________________                                    

EXAMPLE 5

Example 1 was repeated, however instead in ethyltriphenylphosphoniumiodide, tin octoate was used. A modified resin having a final EGC valueof 2022 was obtained instead of 2288.

EXAMPLE 6

Example 1 was repeated, however, using EPIKOTE 834-X-80 (high viscosityliquid epoxy resin produced from bisphenol A and epichlorohydrin; EGC4000; 80% m/m solution in xylene; 200 g) instead of EPIKOTE 828. Thefinal reaction temperature was 160° C. The modified resin had a finalEGC of 1763 mmol/kg and a viscosity of 4.23 Pa.s (measured at aBrookfield viscometer at 23° C./50% r.h.).

EXAMPLES 7-13

Clear lacquers were made using EPIKOTE 828EL, the modified resins madein Examples 2-6 and a physical mixture of Epikote 828EL and thealkylated salicylic acid as used in Examples 1-6 to prepare the modifiedresins. In each of the examples 50 g of resin, ANCAMIDE 2050, acommercially available curing agent and 5 g of ANCAMINE K54(2,4,6-tris(dimethylaminomethyl)phenol, a commercially available curingaccelerator, were used. The Beck Koller gel times (hours) were measuredat 5° C./85% r.h. (softgel time/hard gel time). In Example 13 a blend of50 g resin and 32.6 g of alkyl salicylic acid was used.

    ______________________________________                                        Ex.  Resin      Curing agent                                                                             Gel times                                                                             Appearance                                 ______________________________________                                        7    E 828EL    40.05   g     5.2/12.4                                                                             hazy, tacky                              8    Example 2  17.16   g    3.2/6.7 clear, non-tacky                         9    Example 3  17.89   g    3.5/6.7 clear, non-tacky                         10   Example 4  18.66   g    4.1/7.6 clear, non-tacky                         11   Example 5  15.5    g    1.7/4.8 clear, non-tacky                         12   Example 6  13.2    g    1.8/4.3 clear                                    13   E 828EL/acid                                                                             40.05   g     8.2/19.5                                                                             hazy, tacky                              ______________________________________                                    

EXAMPLES 14 and 15

Example 7 was repeated, however, using EPIKURE F205, a commerciallyavailable curing agent, as curing agent instead of Ancamide 2050. Theamount of resin was 30 g. Ancamine K54, 3 g, was used as curingaccelerator.

    ______________________________________                                        Example    Resin      Curing agent                                                                            Gel times                                     ______________________________________                                        14         E 828EL    16.90   g   5.7/11.3                                    15         Example 2  7.21        3.0/5.9                                     ______________________________________                                    

EXAMPLES 16-18

Examples 1-3 were repeated, however, using 82 g (5 mol percent per epoxygroup) of 3-alkyl substituted salicylic acid.

    ______________________________________                                                                           Viscosity                                  Example  Temperature Final EGC (mmol/kg)                                                                         (Pa.s)                                     ______________________________________                                        16       175         4247          8.07                                       17       140         4298          8.65                                       18       110         4290          6.74                                       ______________________________________                                    

EXAMPLE 19

Example 1 was repeated, however, using EPIKOTE 155 (a glycidatedphenol-formaldehyde novolac; 345 g) instead of EPIKOTE 828. The finalreaction temperature was 175° C. The modified resin had a final EGC of2374 mmol/kg.

EXAMPLES 20-23

In the same way as described for examples 7-13, lacquer layers wereprepared using the modified resins prepared in the examples 16-19.

    ______________________________________                                        Ex.  Resin       Curing Agent                                                                             Gel times                                                                             Appearance                                ______________________________________                                        20   Example 16  31.85 g    4.1/10.7                                                                              clear, almost                                                                 non-tacky                                 21   Example 17  31.85 g    4.1/10.5                                                                              clear, slightly                                                               tacky                                     22   Example 18  31.85 g    4.0/10.6                                                                              clear, slightly                                                               tacky                                     23   Example 19  16.50 g    1.1/2.1 clear, non-                                                                   tacky                                     24   EPIKOTE 155 33.96 g    1.9/3.9 hazy, tacky                               ______________________________________                                    

EPIKOTE, EPIKURE, ANCAMIDE and ANCAMINE are trademarks. EPIKOTE 828 is amedium viscosity bisphenol A based epoxy resin having the structure ofgeneral formula I in which X is hydrogen and n is 0.1. It contains nodiluent. EPIKOTE 828EL is identical with EPIKOTE 828, but having a lowhydrolysable chlorine content. EPIKOTE 834-X-80 is a high viscosityresin of general structure I in which X is hydrogen and n is between 0.1and 0.2, 80% m/m solution in xylene. EPIKOTE 155 is a solid, glycidatedphenol-formaldehyde novolac resin having an EGC of 5650 mmol/kg.ANCAMIDE is a commercially available (Air Products) polyamide curingagent. ANCAMINE is a commercially available (Air Products) amine basedcure accelerator containing 2,4,6-tri(methyl-dimethylamino)phenol.EPIKURE F205 is a curing agent based on EPIKOTE 828 andisophoronediamine. Examples 7, 13, 14 and 24 are comparison examples,not using the modified resins according to the present invention.

We claim:
 1. A curable coating composition comprising a modified epoxyresin and a curing agent, said modified epoxy resin comprising thereaction product of an epoxy resin with less than one mol equivalent perepoxy group of an alkyl or alkenyl substituted, hydroxy substitutedaromatic acid; said curing agent comprising a primary or secondarypolyamine, a polyamide, a polyamidoamine, a polyaminoadduct, apolycarboxylic acid or anhydride thereof, or a polyphenolic compound. 2.The curable coating composition of claim 1, wherein the alkyl or alkenylsubstituted. hydroxy substituted aromatic acid comprises a monoalkyl ordialkyl-substituted benzoic acid.
 3. The curable coating composition ofclaim 2, wherein the acid comprises an alkyl substituted salicylic acid,wherein the alkyl substituent comprises a straight or branched alkylgroup comprising six to twenty-four carbon atoms.
 4. The curable coatingcomposition of claim 1 in which the molar amount of substituted aromaticacid is between about 10 to about 40 percent.
 5. The curable coatingcomposition of claim 1 in which the epoxy resin is a diglycidyl ether ofa bisphenolic compound represented by the general formula I: ##STR2## inwhich A is a divalent hydrocarbon group having 1 to 8 carbon atoms,--C(O)--, --O--, --S--, --S--S--, --S(O)--, --S(O)₂ -- or a covalentbond, each X independently is hydrogen, an alkyl group having 1 to 4carbon atoms, chlorine or bromine, and n has an average value of 0 to12.
 6. The curable coating composition of claim 1 in which the epoxyresin comprises an epoxy novolac resin.
 7. A process for the preparationof a curable coating composition comprising the reaction product of amodified epoxy resin and a curing agent, said modified epoxy resincomprising the reaction product of an epoxy resin with less than 1 molequivalent per epoxy group of an alkyl or alkenyl substituted, hydroxysubstituted aromatic acid; said curing agent comprising a primary orsecondary polyamine, a polyamide, a polyamidoamine, a polyaminoadduct, apolycarboxylic acid or anhydride thereof, or a polyphenolic compound. 8.A process according to claim 7, in which the modified epoxy resinreaction is carried out at a temperature between 100° and 200° C. untilessentially all hydroxy substituted aromatic acid as initially presentin the reaction mixture have reacted and in which as a catalyst is useda tertiary amine, a quaternary ammonium or phosphonium compound or ametal salt.
 9. A metal surface product coated with the curable coatingcomposition according to claim
 1. 10. An curable coating composition ofclaim 1, comprising the reaction product of an epoxy resin with up to 60mol percent per epoxy group of said acid.
 11. The curable coatingcomposition of claim 10, wherein said acid comprises a mono-alkyl,mono-hydroxy aromatic acid.
 12. Curable coating composition of claim 11,comprising 15 mol percent or less of dicarboxylic acids, based on thepresence of monocarboxylic acids.
 13. The curable coating composition ofclaim 11, wherein said alkyl is a straight or branched alkyl groupcontaining 10 to 20 carbon atoms.
 14. The curable coating composition ofclaim 13, wherein said acid comprises a monoalkyl-substituted salicylicacid.
 15. The curable coating composition of claim 14, wherein saidepoxy resin comprises diglycidyl ethers of bisphenol compounds.
 16. Thecurable coating composition of claim 5, wherein A is methylene orisopropylene, X is hydrogen or bromine, and n has an average value from0 to
 2. 17. The curable coating composition of claim 1, wherein saidcuring agent comprises a primary or secondary polyamine, a polyamide, apolyamidoamine, or a polyaminoadduct.
 18. A curable coating compositionof claim 17, wherein the amount of curing agents is about from 0.8 to1.0 equivalents of curing agents per epoxide equivalent.
 19. The processof claim 7, wherein the curing agent comprises a primary or secondarypolyamine, a polyamide, a polyamidoamine, or a polyaminoadduct.
 20. Theprocess of claim 19, wherein the amount of curing agent ranges from 0.8to 1.0 equivalents of curing agent per epoxide equivalent.
 21. Theprocess of claim 7 wherein the curing agent comprises ethylene diamine,diethylene triamine, triethylene tetramine, a dicyandiamide,diaminocyclohexane, or mixtures thereof.